1. Field of the Invention
The present invention relates to an alignment method for positioning objects to be bonded to each other and a mounting method using the alignment method.
2. Discussion of the Related Art
For bonding objects to each other, for example, for bonding a chip to a substrate, relative positions between both objects have to be aligned at a high accuracy. For this alignment, recognition marks for positioning are provided on at least one object, usually, on both objects, the positions of the recognition marks are read by recognition means such as a camera and the recognition marks are positioned to each other, and whereby, the relative relationship in position between both objects is set within a predetermined accuracy.
In such an alignment, for example, in a case where an object is relatively large, recognition marks provided on both end portions thereof and the like are read by moving the recognition means, and based on the reading information, both objects are positioned to each other.
As shown in FIG. 1 for example, a two-sight recognition means 5 having sights in upward and downward directions is inserted between a first object 2 (for example, a chip) held on a head 1 and a second object 4 (for example, a substrate) held on a stage 3. The two-sight recognition means 5 has a two-sight optical system, for example, on an almost identical vertical axis. After a recognition mark A on first object 2 and a recognition mark C on second object 4 are read by moving two-sight recognition means 5, a recognition mark B on first object 2 and a recognition mark D on second object 4 are read by moving two-sight recognition means 5. Based on the reading information, for example, the position and posture of stage 3 are adjusted, thereby setting the relative positional accuracy between both objects within a predetermined accuracy.
In a conventional technology in such an alignment, when upper and lower recognition marks A, C (or B, D) are read, for example, as shown in FIG. 2, after two-sight recognition means 5 is moved to a predetermined reading position P1, a settling time T for complete stop of the recognition means 5 is assured, and the reading accuracy is assured by reading the marks after the complete stop after the settling time T.
However, if the settling time T is assured as described above, because at least about 0.1 to 1 second is taken for the settling time T, there is a limit for shortening the time up to the completion of the alignment, ultimately, a mounting tact for mounting the objects.
Further, if the recognition mark is read at an incomplete stop condition of the object, as shown in FIG. 3 for example, the recognition mark read during the movement may be recognized as a mark F enlarged by being extended in the movement direction X ascribed to the influence of the movement speed, as compared with a positioning recognition mark E recorded at a complete stop condition. In reading of the positioning recognition mark E, this phenomenon occurs, for example, when a shutter speed is set at about 1/100 second or more. If recognized under the condition of mark F thus enlarged based on the recorded recognition mark E, the accuracy for the position recognition reduces.